1. Field of the Invention
The present invention relates to a method and apparatus for attenuating torsional vibration in a drive train of a vehicle, and more particular to such method and apparatus that can attenuate torsional vibration caused upon rapid acceleration and deceleration of the vehicle.
2. Description of the Related Art
When a vehicle is accelerated or decelerated quickly, an output of an engine steeply fluctuates and causes torsional vibration in a drive train between the engine and drive wheels. Such torsional vibration results in back and forth oscillation of the vehicle so that passengers in the vehicle feel uncomfortable. To suppress the torsional vibration, an engine revolution speed that changes with the torsional vibration of the drive train is detected and its change rate is calculated. Using the resulting value, an amount of fuel to be injected into the engine is sequentially modified (increased or decreased) to counterbalance the engine speed fluctuation. This technique is known in the art and disclosed, for instance, in Japanese Patent Application Laid-Open Publication Nos. 60-26242 and 7-324644.
The above mentioned conventional method will be described in detail in reference to FIGS. 8A to 8E of the accompanying drawings.
When an accelerator opening APS (accel position sensor detection) is changed to xe2x80x9copenxe2x80x9d from xe2x80x9cclosedxe2x80x9d (or to a certain value from zero) (FIG. 8A), an engine output steeply increases so that torsional vibration occurs in a drive train operatively coupling an engine with drive wheels. This torsional vibration causes an engine revolution speed RPM to fluctuate (FIG. 8B). A sensor detects the engine revolution speed RPM, and a calculator computes its change rate xcex94RPM (xcex94RPM=RPMxe2x88x92RPM(xe2x88x921)) (FIG. 8C) RPM represents the current engine revolution speed, and RPM(xe2x88x921) represents the engine revolutions speed obtained at previous detection. If xcex94RPM is positive (+), an amount of fuel injection for correction Qacl2 (FIG. 8D) takes a negative value in order to suppress xcex94RPM. On the other hand, if xcex94RPM is a negative value, Qacl2 takes a positive value to reduce xcex94RPM. Such correction value Qacl2 is added to a basic amount of fuel injection Qbase, which is determined by the accelerator opening APS and the engine revolution speed RPM (FIG. 8E). The resulting value Qfnl is the corrected amount of fuel injection (target amount of fuel injection).
The correction value Qacl2 is continuously increased and decreased in accordance with the change of xcex94RPM to counterbalance xcex94RPM and Qfnl is also increased and decreased in the same manner. Further, the basic value Qbase of the final value Qfnl is determined by the accelerator opening and engine speed. Therefore, the fuel is injected in accordance with the accelerator opening APS and it is ensured to provide an engine output in accordance with the accelerator opening. At the same time, a torque sufficient to offset the torsional vibration in the drive train is generated. Accordingly, the torsional vibration is positively attenuated.
Incidentally, the inventor found that the magnitude of torsional vibration in the drive train caused upon change of the accelerator opening APS from xe2x80x9cclosedxe2x80x9d to xe2x80x9copenxe2x80x9d in FIG. 8A is not determined by the difference between the current target value Qfnl (Qbase) at the time of accelerator opened and the previous target value Qfnl(xe2x88x921) at the time of accelerator closed, but by the difference Qabs between the current final value Qfnl (Qbase) and the value Qbad at the time of minimum torque being required by the drive wheels (i.e., at the time of a drive force being first transmitted to the drive wheels from the engine). The inventor also found that the difference Qx between Qbad and Qfnl(xe2x88x921) does not contribute to occurrence of the torsional vibration in the drive train at all.
Therefore, if the correction value Qacl2 described in the preceding paragraphs is determined by the difference Qabs between Qfnl (Qbase) and Qbad, then it is possible to further efficiently attenuate the torsional vibration in the drive train. The value Qbad required to find out the difference Qabs varies with the engine speed RPM and temperature Tw of water flowing in the engine. Thus, if Qbad is obtained from RPM and Tw, Qabs is obtained from Qbad and Qfnl (Qbase), and Qacl2 is determined from Qabs, then it is feasible to efficiently damp the torsional vibration concerned.
In the conventional technique for attenuating the torsional vibration, however, the correction value Qacl2 is never obtained from the difference Qabs. Therefore, there is room for improvement in this regard.
Further, if the above described way of controlling the amount of fuel injection is executed, as illustrated in FIGS. 8A to 8E, it is generally believed that the wave or oscillation of the engine revolution speed change xcex94RPM and the wave of the correction value Qacl2 have reversed shapes of the same period (FIGS. 8C and 8D). However, if it is observed microscopically, the correction value Qacl2 is determined after the change occurs in the engine revolution speed RPM. In actuality, therefore, the wave of the correction value Qacl2 fluctuates at a slightly delayed phase xcex from the xcex94RPM wave. As a result, if the correction value Qacl2 is determined solely from xcex94RPM as in the above described control, the correction made becomes xe2x80x9crun afterxe2x80x9d correction having a time delay corresponding to the phase difference xcex. Consequently, appropriate correction cannot be expected. This results in longer time to be required in torsional vibration attenuation.
On the other hand, the change in the engine revolution speed RPM is caused by increase and decrease of the amount of fuel injection. Specifically, the difference between the amount of fuel injection before acceleration (or deceleration) and the current amount of fuel injection after acceleration/deceleration becomes the cause of fluctuation of the engine revolution speed RPM, i.e., torsional vibration in the drive train. Thus, the difference Qdelta between the last amount of fuel injection Qaclini prior to quick acceleration (or deceleration) of the vehicle and the current basic amount of fuel injection Qbase should be calculated, and then the corrected amount of fuel injection should be determined from this difference Qdelta. By dosing so, the torsional vibration can be promptly damped as compared with the technique of determining the correction value Qacl2 solely from the engine revolution speed change xcex94RPM.
However, the conventional technique of damping the torsional vibration never determines the corrected value from the difference Qdelta Thus, there is also room for improvement in this regard.
An object of the present invention is to overcome the above described problems and make improvements in the above mentioned regards.
According to one aspect of the present invention, there is provided a method of attenuating torsional vibration in a drive train of a vehicle, including the step of detecting engine revolution speed fluctuation that varies with torsional vibration caused in the drive train when the vehicle is quickly accelerated/decelerated, the step of determining a basic amount of fuel injection Qbase from an accelerator opening APS and an engine revolution speed RPM, the step of determining an amount of fuel injection (minimum torque fuel injection) Qbad needed at the time of drive power being first transmitted to drive wheels from an engine based on water temperature Tw and engine revolution speed RPM, the step of calculating a difference Qabs by subtracting the minimum torque fuel injection Qbad from the basic value Qbase, the step of determining a correction value Qacl2 to counterbalance the fluctuation of the engine revolution speed RPM based on the difference Qabs, engine revolution speed RPM, engine revolution speed change xcex94RPM and/or its differential value Dxcex94RPM, and the step of sequentially increasing/decreasing an amount of fuel injection in accordance with the correction value Qacl2, thereby attenuating the torsional vibration.
The difference Qabs between the basic value Qbase and minimum torque fuel injection Qbad is substantially a parameter of determining the magnitude of the torsional vibration occurring in the drive train. This is because the difference Qabs obtained by subtracting the minimum torque fuel injection Qbad at the time of the drive power being first transmitted to the vehicle from the basic fuel injection Qbase indicates how much more (or less) amount of fuel has injected relative to Qbad. In the present invention, therefore, by determining the correction value Qacl2 using this difference Qabs, the fuel is injected in a manner to offset the fluctuation of the engine revolution speed RPM, and consequently the torsional vibration in the drive train is promptly damped.
Since the minimum torque fuel injection Qbad needed to obtain the difference Qabs varies with the engine revolution speed RPM and water temperature Tw, the minimum torque fuel injection Qbad is determined from RPM and Tw, and the difference Qabs is calculated from the minimum torque fuel injection Qbad and the current fuel injection Qfnl (Qbase). If this difference Qabs is used to obtain the correction fuel injection Qacl, the torsional vibration in the drive train is efficiently attenuated even at a time of starting up of the engine at low temperature.
According to another aspect of the present invention, there is provided a method of attenuating torsional vibration in a drive train of a vehicle, including the step of detecting fluctuation in engine revolution speed that varies with torsional vibration in the drive train caused upon quick acceleration or deceleration of the vehicle, the step of determining a basic amount of fuel injection Qbase from an accelerator opening APS and an engine revolution speed RPM, the step of determining an amount of fuel injection (minimum torque fuel injection) Qbad needed at the time of drive power being first transmitted to drive wheels from the engine from water temperature Tw and engine revolution speed RPM, the step of obtaining a difference Qabs by subtracting the minimum torque fuel injection Qbad from the basic value Qbase, the step of determining a correction value Qacl from the difference Qabs and engine revolution speed RPM, the step of determining a second correction value Qacl2 from the first correction value Qacl, engine revolution speed change xcex94RPM and/or its differential value D xcex94RPM to counterbalance the engine revolution speed fluctuation, the step of adding the second correction value Qacl2 and the basic value Qbase to obtain a final amount of fuel injection Qfnl, and the step of sequentially increasing/decreasing an amount of fuel injection in accordance with the final value Qfnl.
According to a third aspect of the present invention, there is provided a method of attenuating torsional vibration in a drive train of a vehicle, including the step of detecting engine revolution speed fluctuation that varies with torsional vibration caused in the drive train when the vehicle is accelerated/decelerated, the step of determining a temporary correction value Qacl2 that counterbalances the fluctuation of engine revolution speed based on engine revolution speed change xcex94RPM and its differential value Dxcex94RPM, the step of determining a correction coefficient QMPX based on difference Qdelta between a final amount of fuel injection Qaclini before acceleration/deceleration and current basic amount of fuel injection Qbase, the step of multiplying Qacl2 by QMPX to obtain a final correction value QaclMPX, the step of sequentially increasing/decreasing a target amount of fuel injection Qfnl in accordance with QaclMPX, and the step of injecting fuel of the target amount Qfnl increased/decreased into the engine, thereby attenuating the torsional vibration.
The difference Qdelta between the before-acceleration/deceleration final value of fuel injection Qaclini and the current basic fuel injection Qbase is, as mentioned above, the cause of the fluctuation of the engine revolution speed RPM, i.e., the cause of torsional vibration in the drive train. Therefore, the correction coefficient QMPX is determined from this difference Qdelta, and the temporary correction value Qacl2 is multiplied by this coefficient QMPX to obtain the ultimate correction value QaclMPX. The resulting value QaclMPX is an adjustment value prepared in consideration of not only the change xcex94RPM of the engine revolution speed RPM and its differential value Dxcex94RPM, but also the difference Qdelta that is the cause of the torsional vibration in the drive train. Therefore, by sequentially increasing/decreasing the target amount of fuel injection Qfnl in accordance with this adjustment value QaclMPX, the engine revolution speed fluctuation, i.e., the torsional vibration in the drive train can promptly be attenuated.
According to a fourth aspect of the present invention, there is provided a method of attenuating torsional vibration in a drive train of a vehicle by sequentially increasing/decreasing an amount of fuel to be injected into an engine, including the step of detecting engine revolution speed fluctuation that varies with torsional vibration caused in the drive train when the vehicle is accelerated/decelerated, the step of determining a basic amount of fuel injection Qbase from an accelerator opening APS and engine revolution speed RPM, the step of determining a temporary correction value Qacl2 from engine revolution speed change xcex94RPM and/or its differential value Dxcex94RPM to offset the fluctuation of engine revolution speed RPM, the step of determining a correction coefficient QMPX based on difference Qdelta between a final amount of fuel injection Qaclini before acceleration/deceleration and current basic amount of fuel injection Qbase, the step of multiplying Qacl2 by QMPX to obtain a final correction value QaclMPX, the step of adding QaclMPX and Qbase to obtain a target amount of fuel injection Qfnl, and the step of injecting fuel of the target amount Qfnl into the engine.
The method may further include the step of determining whether the engine revolution speed fluctuation occurs upon shifting up/down of a transmission, and the step of adding the basic amount of fuel injection Qbase and correction value Qacl2 to obtain a target amount Qfnl of fuel injection, if it is determined that the engine revolution speed fluctuation occurs upon shifting up/down (transmission gear position change). If, on the other hand, it is determined that the engine revolution speed fluctuation does not take place upon shifting up/down, then the correction value QaclMPX is added to the basic value Qbase to obtain the target value Qfnl.
The engine revolution speed fluctuation is not always caused by increase/decrease in the amount of fuel injection. For instance, it may be caused by shifting up or down. If such is the case, the increase/decrease of the fuel injection does not relate to the generation of the engine revolution speed fluctuation (generation of torsional vibration in the drive train) at all. Thus, if the target amount of fuel injection is adjusted in accordance with the increase/decrease of the fuel injection in such a case, the engine is forced to rotate unnecessarily. As a result, longer time is required until the torsional vibration completely attenuates. In the present invention, therefore, the target amount of fuel injection is not adjusted in accordance with the increase/decrease of the fuel injection if the engine revolution speed fluctuation is caused upon shifting up/down.
In other words, when the engine revolution speed fluctuation takes places due to the shift changing, the correction value Qacl2, which is determined based on the engine revolution speed change xcex94RPM and/or its differential value Dxcex94RPM without considering the increase/decrease of the fuel injected, is added to the basic value Qbase to obtain Qfnl. When the engine revolution speed fluctuation occurs while no shift up/down operation is being performed, Qfnl is obtained by adding Qbase and QaclMPX, which is determined in consideration of the increase/decrease of the fuel injection.
According to a fifth aspect of the present invention, there is provided an apparatus for attenuating torsional vibration in a drive train coupling an engine with drive wheels, including means for detecting engine revolution speed fluctuation that varies with torsional vibration caused in the drive train when the vehicle is accelerated/decelerated, means for determining a basic amount of fuel injection Qbase from an accelerator opening APS and an engine revolution speed RPM, means for determining an amount of fuel injection (minimum torque fuel injection) Qbad needed at the time of drive power being first transmitted to the drive wheels from the engine based on water temperature Tw and engine revolution speed RPM, means for calculating a difference Qabs by subtracting the minimum torque fuel injection Qbad from the basic value Qbase, means for determining a correction value Qacl2 to counterbalance the fluctuation of the engine revolution speed RPM based on the difference Qabs, engine revolution speed RPM, engine revolution speed change xcex94RPM and/or its differential value Dxcex94RPM, and means for sequentially increasing/decreasing an amount of fuel injection in accordance with the correction value Qacl2, thereby attenuating the torsional vibration.
Additional objects, benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the embodiments and the appended claims, taken in conjunction with the accompanying drawings.